Although dissolved organic matter (DOM) has a substantial influence on biogeochemical processes relevant to erosion in agricultural ecosystems, the mechanisms underlying the dynamics and biodegradation of DOM in eroding landscapes are yet to clarified. In this study, we examined the changes in dissolved organic carbon (DOC), profile distribution, biodegradation, and chemical characteristics associated with erosion in a Mollisol agricultural landscape. The results showed that DOC content in the mid-slope was significantly higher than that in the down-slope, particularly at depths of 40–100 cm. The higher humification index and low biological index indicated that the DOM in the depositional position was characterized by a higher humic content compared to the up-slope positions. The up-slope samples were found to contain larger amounts of protein-like substances, whereas the mid- and down-slope soils comprised a larger proportion of anthropogenic humic-like materials, indicating that DOM in the up-slope soil was primarily microbial-derived. For the topsoils, the activities of β-glucosidase and cellulase were highest in the down-slope both before and after incubation, thereby suggesting that the deposition was conducive to the secretion of these enzymes by soil microbes. Overall, our observations indicated that erosion and deposition had a significant effect on the chemical composition and biodegradation pathways of DOM in soil profiles. These findings provided detailed information on the heterogeneous DOM characteristics at the molecular level, as well as DOC effects on environmental behavior in agricultural eroding environments.

尽管溶解有机物(DOM) 对与农业生态系统侵蚀相关的生物地球化学过程有重大影响，但 DOM 在侵蚀景观中的动态和生物降解机制尚未阐明。在本研究中，我们研究了Mollisol农业景观中与侵蚀相关的溶解有机碳 (DOC)、剖面分布、生物降解和化学特征的变化。结果表明，中坡的 DOC 含量显着高于下坡，特别是在 40-100 厘米的深度。更高的屈辱指数和低生物指数表明，与上坡位置相比，沉积位置的 DOM 具有较高的腐殖质含量。上坡样品被发现含有大量的蛋白质类物质，而中坡和下坡土壤包含较大比例的人为类腐殖质物质，表明上坡土壤中的 DOM 主要是微生物-衍生的。对于表土，β-葡萄糖苷酶和纤维素酶在培养前后均在下坡处最高，表明沉积有利于土壤微生物分泌这些酶。总的来说，我们的观察表明，侵蚀和沉积对土壤剖面中 DOM 的化学成分和生物降解途径有显着影响。这些发现提供了分子水平上异质 DOM 特征的详细信息，以及 DOC 对农业侵蚀环境中环境行为的影响。